1. Field of the Invention
The present invention relates to an outboard motor.
2. Description of the Related Art
The evaluation of misfires in engines is generally known in the technical field of automobiles. Moreover, the learning of parameters for correcting parameter tolerances for conducting misfire evaluations is also well known. For example, a control device disclosed in Japanese Patent Laid-open No. 2008-111354 computes an angular speed of a crankshaft on the basis of the output of a pulse generator. Then, a learning correction coefficient for correcting a speed parameter is derived in accordance with an average speed parameter that indicates the angular speed. Japanese Patent Laid-open No. H07-259631 discloses a misfire detection device that updates a correction coefficient at predetermined cycles. Patent Japanese Patent Laid-open No. H10-077898 discloses a misfire diagnostic device that computes a learning value for each of a high load region and a low load region. Patent Japanese Patent Laid-open No. H07-63048 discloses a misfire diagnostic device that computes a first correction coefficient and a second correction coefficient. That is, the misfire diagnostic device improves the learning accuracy by conducting learning in two stages. Patent Japanese Patent Laid-open No. H09-32626 discloses a misfire diagnostic device that prohibits a misfire evaluation when a currently measured crank angle zone differs from a previously measured crank angle zone. Various methods have been proposed for improving the evaluation accuracy of misfires in the technical field of automobiles as described in the above documents. Countermeasures for stopping mis-evaluations of misfires are also disclosed.
However, the above types of misfire evaluations are not conducted for outboard motors as of yet. For example, Japanese Patent Laid-open No. 2004-36420 discloses an engine breakdown diagnostic system for an engine in an outboard motor. This breakdown diagnostic system records information relating to the state of the engine under operation as a history for judging the presence or absence of a breakdown ex post facto, but does not conduct a misfire evaluation.
Generally, outboard motors are mounted onto a boat selected by a user or a boat dealer after being shipped from the manufacturer. Engine characteristics change in accordance with the size of the boat onto which the outboard motor is mounted since the outboard motor may be mounted onto various sizes of boats. In addition, the propeller attached to the outboard motor may be replaced. The engine characteristics change in accordance with the propeller specifications since propellers attached to outboard motors may include various specifications. Therefore, the engine characteristics of an outboard motor are not always the same when shipped from the manufacturer and when used by the user. As a result, learning for correcting variations in engine characteristics due to individual differences in engines must be conducted when actually operating the boat in a state in which the outboard motor is mounted onto the boat and a propeller is attached to the outboard motor. As a result, implementing learning before shipping the outboard motor is impossible. Conversely, when learning is implemented by the user after shipping of the outboard motor, there is a possibility that the learning may not be conducted accurately due to the method of the learning. Further, there is a possibility that faulty evaluations of misfires may continuously occur if the user does not implement the learning.